371 research outputs found
Abundances on the Main Sequence of Omega Centauri
Abundance ratios of carbon, nitrogen and strontium relative to iron,
calculated using spectrum synthesis techniques, are given for a sample of main
sequence and turnoff stars that belong to the globular cluster omega Centauri.
The variations of carbon, nitrogen and/or strontium show several different
abundance patterns as a function of [Fe/H]. The source of the
enhancements/depletions in carbon, nitrogen and/or strontium may be enrichment
from asymptotic giant branch stars of low (1--3 solar masses) and intermediate
(3--8 solar masses) mass. Massive rotating stars which produce excess nitrogen
without carbon and oxygen overabundances may also play a role. These abundances
enable different contributors to be considered and incorporated into the
evolutionary picture of omega Cen.Comment: 43 Pages, 13 Figures. Accepted for publication in Ap
Luminous Red Galaxy Clustering at z~0.7 - First Results using AAOmega
We report on the AAT-AAOmega LRG Pilot observing run to establish the
feasibility of a large spectroscopic survey using the new AAOmega instrument.
We have selected Luminous Red Galaxies (LRGs) using single epoch SDSS
riz-photometry to i<20.5 and z<20.2. We have observed in 3 fields including the
COSMOS field and the COMBO-17 S11 field, obtaining a sample of ~600 redshift
z>=0.5 LRGs. Exposure times varied from 1 - 4 hours to determine the minimum
exposure for AAOmega to make an essentially complete LRG redshift survey in
average conditions. We show that LRG redshifts to i<20.5 can measured in
approximately 1.5hr exposures and present comparisons with 2SLAQ and COMBO-17
(photo-)redshifts. Crucially, the riz selection coupled with the 3-4 times
improved AAOmega throughput is shown to extend the LRG mean redshift from
z=0.55 for 2SLAQ to z=0.681+/- 0.005 for riz-selected LRGs. This extended range
is vital for maximising the S/N for the detection of the baryon acoustic
oscillations (BAOs). Furthermore, we show that the amplitude of LRG clustering
is s_0 = 9.9+/-0.7 h^-1 Mpc, as high as that seen in the 2SLAQ LRG Survey.
Consistent results for the real-space amplitude are found from projected and
semi-projected correlation functions. This high clustering amplitude is
consistent with a long-lived population whose bias evolves as predicted by a
simple ``high-peaks'' model. We conclude that a redshift survey of 360 000 LRGs
over 3000deg^2, with an effective volume some 4 times bigger than previously
used to detect BAO with LRGs, is possible with AAOmega in 170 nights.Comment: 12 pages, 7 figures, 8 tables, minor changes, matches published
versio
Verbal thinking and inner speech use in autism spectrum disorder
The extent to which cognition is verbally mediated in neurotypical individuals is the subject of debate in cognitive neuropsychology, as well as philosophy and psychology. Studying “verbal thinking” in developmental/neuropsychological disorders provides a valuable opportunity to inform theory building, as well as clinical practice. In this paper, we provide a comprehensive, critical review of such studies among individuals with autism spectrum disorder (ASD). ASD involves severe social-communication deficits and limitations in cognitive/behavioural flexibility. The prevailing view in the field is that neither cognition nor behaviour is mediated verbally in ASD, and that this contributes to diagnostic features. However, our review suggests that, on the contrary, most studies to date actually find that among people with ASD cognitive task performance is either a) mediated verbally in a typical fashion, or b) not mediated verbally, but at no obvious cost to overall task performance. Overall though, these studies have methodological limitations and thus clear-cut conclusions are not possible at this stage. The aim of the review is to take stock of existing empirical findings, as well as to help develop the directions for future research that will resolve the many outstanding issues in this field
The WiggleZ Dark Energy Survey: Survey Design and First Data Release
The WiggleZ Dark Energy Survey is a survey of 240,000 emission line galaxies
in the distant universe, measured with the AAOmega spectrograph on the 3.9-m
Anglo-Australian Telescope (AAT). The target galaxies are selected using
ultraviolet photometry from the GALEX satellite, with a flux limit of NUV<22.8
mag. The redshift range containing 90% of the galaxies is 0.2<z<1.0. The
primary aim of the survey is to precisely measure the scale of baryon acoustic
oscillations (BAO) imprinted on the spatial distribution of these galaxies at
look-back times of 4-8 Gyrs. Detailed forecasts indicate the survey will
measure the BAO scale to better than 2% and the tangential and radial acoustic
wave scales to approximately 3% and 5%, respectively.
This paper provides a detailed description of the survey and its design, as
well as the spectroscopic observations, data reduction, and redshift
measurement techniques employed. It also presents an analysis of the properties
of the target galaxies, including emission line diagnostics which show that
they are mostly extreme starburst galaxies, and Hubble Space Telescope images,
which show they contain a high fraction of interacting or distorted systems. In
conjunction with this paper, we make a public data release of data for the
first 100,000 galaxies measured for the project.Comment: Accepted by MNRAS; this has some figures in low resolution format.
Full resolution PDF version (7MB) available at
http://www.physics.uq.edu.au/people/mjd/pub/wigglez1.pdf The WiggleZ home
page is at http://wigglez.swin.edu.au
All-sky search for periodic gravitational waves in LIGO S4 data
We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50-1000 Hz and with the frequency's
time derivative in the range -1.0E-8 Hz/s to zero. Data from the fourth LIGO
science run (S4) have been used in this search. Three different semi-coherent
methods of transforming and summing strain power from Short Fourier Transforms
(SFTs) of the calibrated data have been used. The first, known as "StackSlide",
averages normalized power from each SFT. A "weighted Hough" scheme is also
developed and used, and which also allows for a multi-interferometer search.
The third method, known as "PowerFlux", is a variant of the StackSlide method
in which the power is weighted before summing. In both the weighted Hough and
PowerFlux methods, the weights are chosen according to the noise and detector
antenna-pattern to maximize the signal-to-noise ratio. The respective
advantages and disadvantages of these methods are discussed. Observing no
evidence of periodic gravitational radiation, we report upper limits; we
interpret these as limits on this radiation from isolated rotating neutron
stars. The best population-based upper limit with 95% confidence on the
gravitational-wave strain amplitude, found for simulated sources distributed
isotropically across the sky and with isotropically distributed spin-axes, is
4.28E-24 (near 140 Hz). Strict upper limits are also obtained for small patches
on the sky for best-case and worst-case inclinations of the spin axes.Comment: 39 pages, 41 figures An error was found in the computation of the C
parameter defined in equation 44 which led to its overestimate by 2^(1/4).
The correct values for the multi-interferometer, H1 and L1 analyses are 9.2,
9.7, and 9.3, respectively. Figure 32 has been updated accordingly. None of
the upper limits presented in the paper were affecte
Search for gravitational waves from binary inspirals in S3 and S4 LIGO data
We report on a search for gravitational waves from the coalescence of compact
binaries during the third and fourth LIGO science runs. The search focused on
gravitational waves generated during the inspiral phase of the binary
evolution. In our analysis, we considered three categories of compact binary
systems, ordered by mass: (i) primordial black hole binaries with masses in the
range 0.35 M(sun) < m1, m2 < 1.0 M(sun), (ii) binary neutron stars with masses
in the range 1.0 M(sun) < m1, m2 < 3.0 M(sun), and (iii) binary black holes
with masses in the range 3.0 M(sun)< m1, m2 < m_(max) with the additional
constraint m1+ m2 < m_(max), where m_(max) was set to 40.0 M(sun) and 80.0
M(sun) in the third and fourth science runs, respectively. Although the
detectors could probe to distances as far as tens of Mpc, no gravitational-wave
signals were identified in the 1364 hours of data we analyzed. Assuming a
binary population with a Gaussian distribution around 0.75-0.75 M(sun), 1.4-1.4
M(sun), and 5.0-5.0 M(sun), we derived 90%-confidence upper limit rates of 4.9
yr^(-1) L10^(-1) for primordial black hole binaries, 1.2 yr^(-1) L10^(-1) for
binary neutron stars, and 0.5 yr^(-1) L10^(-1) for stellar mass binary black
holes, where L10 is 10^(10) times the blue light luminosity of the Sun.Comment: 12 pages, 11 figure
Search for gravitational-wave bursts in LIGO data from the fourth science run
The fourth science run of the LIGO and GEO 600 gravitational-wave detectors,
carried out in early 2005, collected data with significantly lower noise than
previous science runs. We report on a search for short-duration
gravitational-wave bursts with arbitrary waveform in the 64-1600 Hz frequency
range appearing in all three LIGO interferometers. Signal consistency tests,
data quality cuts, and auxiliary-channel vetoes are applied to reduce the rate
of spurious triggers. No gravitational-wave signals are detected in 15.5 days
of live observation time; we set a frequentist upper limit of 0.15 per day (at
90% confidence level) on the rate of bursts with large enough amplitudes to be
detected reliably. The amplitude sensitivity of the search, characterized using
Monte Carlo simulations, is several times better than that of previous
searches. We also provide rough estimates of the distances at which
representative supernova and binary black hole merger signals could be detected
with 50% efficiency by this analysis.Comment: Corrected amplitude sensitivities (7% change on average); 30 pages,
submitted to Classical and Quantum Gravit
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